Amine substituted hydrocarbon polymer dispersant lubricating oil additives

ABSTRACT

Dispersant lubricating oil additives are prepared by reacting oil-soluble dispersant compositions containing at least one primary or secondary amino group with SO 2 .

This is a division of application Ser. No. 966,179, filed Dec. 4, 1978U.S. Pat. No. 4,275,006.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Lubricating oil additives are prepared by reacting a dispersantcomposition containing at least one primary or secondary amino groupwith SO₂.

2. Description of the Prior Art

Most commercial lubricating oils now contain disperant additives to helpkeep the engine clean by dispersing sludge and varnish-forming depositsin the oil. Many of these additives contain nitrogen. Many recentlydeveloped additives combine dispersant activity with viscosity indeximproving characteristics. Additives which function in this manner arevariously known in the art as detergent additives or dispersantadditives. For the purposes of this description, the term "dispersant"is intended to include both dispersant and detergent additives.

U.S. Pat. No. 3,741,998 teaches the preparation of aqueous detergentsvia a two-stage process which comprises: (1) forming an adduct of sulfurdioxide or sulfur trioxide and a quaternary amine; and (2) reacting thisadduct with an aziridinyl compound.

U.S. Pat. No. 3,843,722 teaches the preparation of alkyl amidosulfinicacid (bis-alkylamine) salts, useful as analytical reagents, by reactingan amine containing 1-20 carbon atoms with SO₂.

SUMMARY OF THE INVENTION

It has now been found that the dispersant performance in both diesel andgasoline engines of nitrogen-containing lubricating oil additives havingat least one primary or secondary amino group is improved by reactionwith SO₂. The resistance to oxidation of lubricating oil compositionscontaining the product is also improved while the corrosivity to leadbearings is reduced. In addition, while dispersants may adversely affectwear performance in formulated oils, the SO₂ -treated dispersants do notdegrade and may also improved wear performance.

DETAILED DESCRIPTION OF THE INVENTION

The reaction of SO₂ with the nitrogen-containing dispersants describedbelow leads, it is believed, to the formation of amidosulfurous acidsand amidosulfurous acid ammonium salts. The salts are formed when onemol of SO₂ reacts with two basic nitrogens, either in the same ordifferent molecules. While other structures are possible, these saltsare believed to have one of the general formulas (where R representshydrogen or a hydrocarbyl-based substituent): ##STR1## The basicnitrogens are either primary amino (--NH₂) or secondary amino (═NH)groups.

The Nitrogen-Containing Dispersants

The dispersants whose performance is improved by the process of thisinvention must contain at least one basic nitrogen and have at leastone >NH group. The particular dispersant used and its structure ormethod of preparation is not critical to the invention so long as thedispersant contains at least one primary or secondary amino group. Theessence of this invention resides in the surprising discovery thattreating the dispersant with SO₂ improves the dispersant properties,while improving resistance to oxidation and decreasing the corrosivityto lead bearings. The dispersants include hydrocarbyl succinimideshaving at least one additional amino group, hydrocarbyl-substitutedpolyamines, Mannich bases, borated Mannich bases, hydrocarbylsulfonamides having at least one additional amino group,N-alkylaminophosphoramides, polyoxyalkylene polyamines, andamino-decorated hydrocarbon polymers useful as dispersant-viscosityindex improvers.

Succinimide compositions useful for preparing the additives of thisinvention are well known in the art. A general method for theirpreparation is found in U.S. Pat. Nos. 3,219,666, 3,172,892, and3,272,746, the disclosures of which are incorporated herein byreference. These compositions are prepared by reacting an alkyl oralkenyl succinic acid or anhydride with a nitrogen-containing compound.For the purposes of this invention, the nitrogen-containing compoundmust be of a type such that the resultant product contains at least oneprimary or secondary amino group. The succinimide may be of the typecommonly known as mono- or bis-succinimide. Preferred nitrogen compoundsare those commonly known as ethylene amines. Particularly preferred aretriethylenetraamine and tetraethylenepentamine. The preferred alkyl oralkenyl groups contain from 50 to 300 carbon atoms and is mostpreferably polyisobutenyl.

The hydrocarbyl-substituted polyamines are also well known. A method fortheir preparation is found in U.S. Pat. No. 3,565,804, the disclosure ofwhich is hereby incorporated by reference. These compounds arehigh-molecular-weight hydrocarbyl-N-substituted alkylene polyamines.They have an average molecular weight in the range of 600-10,000 moreusually in the range of about 750-5000.

The hydrocarbyl radical may be aliphatic or aliphatic and, except foradventitious amounts of aromatic structure in petroleum mineral oils,will be free of aromatic unsaturation. The hydrocarbyl groups willnormally be branched-chain aliphatic, having 0-2 sites of unsaturation,and preferably from 0-1 site of ethylenic unsaturation. The hydrocarbylgroups are preferably derived from petroleum mineral oil, orpolyolefins, either homopolymers or higher-order polymers, or 1-olefinsof from 2-6 carbon atoms. Ethylene is preferably copolymerized with ahigher olefin to insure oil solubility.

Illustrative polymers include polypropylene, polyisobutylene,poly-1-butene, etc. The polyolefin group will normally have at least 1branch per 6 carbon atoms along the chain, preferably at least 1 branchper 4 carbon atoms along the chain, and it is particularly preferredthat there be from 0.3 to 1 branch per carbon atom along the chain.These branched-chain hydrocarbons are readily prepared by thepolymerization of olefins of from 3-6 carbon atoms and preferably fromolefins of from 3-4 carbon atoms.

In preparing the compositions of this invention, rarely will a singlecompound having a defined structure be employed. With both polymers andpetroleum-derived hydrocarbon groups, the composition is a mixture ofmaterials having various structures and molecular weights. Therefore, inreferring to molecular weight, average molecular weights are intended.Furthermore, when speaking of a particular hydrocarbon group, it isintended that the group include the mixture that is normally containedwithin materials which are commercially available. For example,polyisobutylene is known to have a range of molecular weights and mayinclude small amounts of very-high-molecular-weight materils.

Similarly, commercially available alkylene polyamines are frequentlymixtures of various alkylene polyamines having one or two speciesdominating. Finally, in preparing the compounds of this invention, wherethe various nitrogen atoms of the alkylene polyamine are not equivalent,the product will be a mixture of the various possible isomers.

Particularly preferred polyamines are prepared from polyisobutenylchloride and ethylenediamine or triethylenetetraamine.

The Mannich bases used for preparing the additives of this invention arealso well known. Representative types of Mannich bases are described inU.S. Pat. Nos. 3,741,896, 3,539,633 and 3,649,229, the disclosures ofwhich are hereby incorporated by reference. In general, the Mannichbases are prepared by reacting an alkylphenol, formaldehyde, and a mono-or polyamine. The Mannich base may be borated by reacting with, e.g., aboron halide, boric acid, or an ester of boric acid. Preferred aminesfor use in forming the Mannich base are methylamine and ethyleneaminessuch as ethylenediamine, diethylenetriamine, and triethylenetetraamine.

The hydrocarbyl sulfonamides for use in preparing the additives of thisinvention are described in U.S. Ser. No. 644,474, filed Dec. 29, 1975,the disclosure of which is hereby incorporated by reference. Thesulfonamides are preferably prepared from a hydrocarbyl sulfonylchloride and an amine. Particularly preferred are the reaction productsof polyisobutenyl-sulfonyl chloride containing 50 to 300 carbon atomsand an ethylene amine such as diethylenetriamine, triethylenetetraamine,and tetraethylenepentamine.

The polyoxyalkylene polyamines can be prepared by forming anoxyalkylenated chloroformate and then reacting with an amine.Dispersants of this type are disclosed in copending U.S. Ser. Nos.914,427, 917,150 and 891,879, the entire disclosures of which are herebyincorporated by reference.

Amino-decorated hydrocarbon polymers useful as dispersant viscosityindex improvers are usually prepared by treating a hydrocarbon polymerhaving a viscosity index improving characteristics, such as anethylene-propylene copolymer or terpolymer, either chemically ormechanically to generate active sites and then reacting with an amine orpolyamine. Typical products are prepared by oxidizing the copolymer orterpolymer and reacting with an amine as shown in U.S. Pat. No.3,769,216 or with an amine or an aldehyde as shown in U.S. Pat. No.3,872,019, the disclosures of which are hereby incorporated byreference.

Similarly, other primary or secondary amine-substituted polymers used asviscosity-index improvers may be used as starting materials for theadditives of the invention. Such polymers include amine-grafted acrylicpolymers and copolymers and copolymers wherein one monomer contains atleast one amino group. Typical compositions are described in BritishPat. No. 1,488,382, U.S. Pat. Nos. 4,089,794 and 4,025,452, thedisclosures of which are incorporated herein be reference.

The additives of this invention are prepared by reacting a dispersantcontaining at least one primary or secondary amine group with sulfurdioxide. The reaction is carried out at a temperature of from 20°-200°C., preferably 80° to 150° C., by introducing sulfur dioxide into asolution of the dispersant composition in an inert diluent such aslubricating oil, xylenes, and the like. Usually 1 mol sulfur dioxide maybe introduced for each 2 mols of basic nitrogen in the dispersantcomposition. However, from about 0.2 to about 2.0 mols of SO₂ per 2 molsof basic nitrogen may be used to prepare the product of this invention.The rate of the reaction is dependent upon temperature and the rate ofintroduction of SO₂. The reaction proceeds substantially to completionin from 0.1 to 100 hours. While the reaction proceeds satisfactorily atatmospheric pressure, higher or lower pressures may be used, if desired.

The lubricating oils of this invention contain an oil of lubricatingviscosity and from 0.1 to 10% by weight of the additive of thisinvention.

Additive concentrates are also included within the scope of thisinvention. They usually include from about 90 to 10 weight percent of anoil of lubricating viscosity and are normally formulated to have about10 times the additive concentration that would be used in the finishedlubricating oil composition. Typical concentrates contain 10-90% byweight of the additive of this invention. The concentrates containsufficient diluent to make them easy to handle during shipping andstorage. Suitable diluents for the concentrates include any inertdiluent, preferably an oil of lubricating viscosity, so that theconcentrate may be readily mixed with lubricating oils to preparelubricating oil compositions. Suitable lubricating oils which can beused as diluents typically have viscosities in the range from about 35to about 5000 Saybolt Universal Seconds (SUS) at 100° F. (38° C.),although any oil of lubricating viscosity can be used.

A variety of lubricating oils can be used to prepare a lubricating oilcomposition or concentrate. These oils are of lubricating viscosityderived from petroleum or synthetic sources.

Natural oils include animal oils and vegetable oils (e.g., castor oil,lard oil) as well as liquid petroleum oils and solvent-treated oracid-treated mineral lubricating oils of the paraffinic, naphthenic ormixed paraffinic-naphthenic types. Oils of lubricating viscosity derivedfrom coal or shale are also useful base oils. Synthetic lubricating oilsinclude hydrocarbon oils and halosubstituted hydrocarbon oils such aspolymerized and interpolymerized olefins [e.g., polybutylenes,polyproylenes, polypropylene-isobutylene copolymers, chlorinatedpolybutylenes, poly(1-hexenes), poly(1-octenes), poly(1-decenes), etc.,and mixtures thereof]; alkylbenzenes [e.g., dodecylbenzenes,tetradecylbenzenes, dinonylbenzenes, di-(2-ethylhexyl)benzenes, etc.];polyphenyls [e.g., biphenyls, terphenyls, alkylated polyphenyls, etc.],alkylated diphenyl ethers and alkylated diphenyl sulfides and thederivatives, analogs and homologs thereof, and the like.

Alkylene oxide polymers and interpolymers and derivatives thereof wherethe terminal hydroxyl groups have been modified by esterification,etherification, etc., constitute another class of known syntheticlubricating oils. These are exemplified by the oils prepared throughpolymerization of ethylene oxide or propylene oxide, the alkyl and arylethers of these polyalkylene polymers (e.g., methylpolyisopropyleneglycol ether having an average molecular weight of 1000, diphenyl etherof polypropylene glycol having a molecular weight of 500-1000, diethylether of polypropylene glycol having a molecular weight of 1000-1500,etc.) or mono- and polycarboxylic esters thereof, for example the aceticacid esters, mixed C₃ -C₈ fatty acid esters, or the C₁₃ Oxo acid diesterof tetraethylene glycol.

Another suitable class of synthetic lubricating oils comprises theesters of dicarboxylic acids (e.g., phthalic acid, succinic acid, alkylsuccinic acids and alkenyl succinic acids, maleic acid, azelaic acid,suberic acid, sebacic acid, fumaric acid, adipic acid, linoleic aciddimer, malonic acid, alkyl malonic acids, alkenyl malonic acids, etc.)with a variety of alcohols (e.g., butyl alcohol, hexyl alcohol, dodecylalcohol, 2-ethylhexyl alcohol, ethylene glycol, diethylene glycolmonoether, propylene glycol, etc.). Specific examples of these estersinclude dibutyl adipate, di-(2-ethylhexyl) sebacate, di-n-hexylfumarate, dioctyl sebacate, diisooctyl azelate, diisodecyl azelate,dioctyl phthalate, didecyl phthalate, dieicosyl sebacate, the2-ethylhexyl diester of linoleic acid dimer, the complex ester formed byreacting one mol of sebacic acid with two mols of tetraethylene glycoland two mols of 2-ethylhexanoic acid, and the like.

Esters useful as synthetic oils also include those made from C₅ to C₁₂monocarboxylic acids and polyols and polyol ethers such as neopentylglycol, trimethylolpropane, pentaerythritol, dipentaerythritol,tripentaerythritol, etc.

Silicon-based oils such as the polyalkyl-, polyaryl-, polyalkoxy-, orpolyaryloxy-siloxane oils and silicate oils comprise another usefulclass of synthetic lubricants [e.g., tetraethyl silicate, tetraisopropylsilicate, tetra-(2-ethylhexyl) silicate, tetra-(4-methyl-2-ethylhexyl)silicate, tetra-(-p-tert-butylphenyl) silicate,hexyl-(4-methyl-2-pentoxy) disiloxane, poly-(methyl) siloxanes,poly(methylphenyl) siloxanes, etc.]. Other synlubricating oils includeliquid esters of phosphorus-containing acids (e.g., tricresyl phosphate,trioctyl phosphate, diethyl ester of decylphosphonic acid, etc.),polymeric tetrahydrofurans and the like.

Unrefined, refined and rerefined oils (and mixtures of each with eachother) of the type disclosed hereinabove can be used in the lubricantcompositions of the present invention. Unrefined oils are those obtaineddirectly from a natural or synthetic source without further purificationtreatment. For example, a shale oil obtained directly from retortingoperations, a petroleum oil obtained directly from distillation or esteroil obtained directly from an esterification process and used withoutfurther treatment would be an unrefined oil. Refined oils are similar tothe unrefined oils, except they have been further treated in one or morepurification steps to improve one or more properties. Many suchpurification techniques are known to those of skill in the art such assolvent extraction, acid or base extraction, filtration, percolation,etc. Rerefined oils are obtained by processes similar to those used toobtain refined oils applied to refined oils which have been already usedin service. Such rerefined oils are also known as reclaimed orreprocessed oils, and often are additionally processed by techniquesdirected to removal of spent additives and oil breakdown products.

Other conventional additives which can be used in combinations with theadditive composition of this invention include oxidation inhibitors,rust inhibitors, antifoam agents, viscosity index improvers, pour-pointdepressants, dispersants and the like. These include such compositionsas chlorinated wax, benzyl disulfide, sulfurized olefins, sulfurizedterpene, phosphorus esters such as trihydrocarbon phosphites, metalthiocarbamates such as zinc dioctyldithiocarbamate, metal phosphorusdithioates such as zinc dioctylphosphorodithioate, polyisobutylenehaving an average molecular weight of 100,000, etc.

The lubricating oil compositions of the invention are useful forlubricating internal combustion engines, automatic transmissions and asindustrial oils such as hydraulic oils, heat-transfer oils, torquefluids, etc. The lubricating oils can not only lubricate the enginesbut, because of their dispersancy properties, help maintain a highdegree of cleanliness of the lubricated parts.

EXAMPLES

The following examples are provided to illustrate the invention. It isto be understood that they are provided for the sake of illustrationonly and not as a limitation on the scope of the invention.

EXAMPLE 1

To a 3-liter reaction flask was added 880 g of a commercial succinimidedispersant composition prepared from polyisobutenyl succinic anhydride(where the polyisobutenyl group has a number average molecular weight ofabout 980) and tetraethylenepentaamine and 1120 g diluent lubricatingoil. The mixture was heated to 150° C. under nitrogen with stirring. Theproduct was then sparged with SO₂ at the rate of 220 cc SO₂ /minute for150 minutes followed by sparging with nitrogen for 150 minutes at 150°C. The product weighed 2048 g (including oil) and contained 1.99% N and1.78% S.

EXAMPLE 2

Following the procedure of Example 1, 1000 g of a commercial succinimidedispersant composition prepared from polyisobutenyl succinic anhydride(where the polyisobutenyl group has a number average molecular weight of980) and triethylenetetraamine in 1000 g lubricating oil diluent wasreacted with SO₂ at the rate of 220 cc SO₂ /-minute for 180 minutes toyield 2054 g product (including oil) containing 1.94% N and 1.56% S.

EXAMPLE 3

To a 3-liter reaction flask was added 600 g of a commercial hydrocarbylamine detergent prepared from polyisobutenyl chloride (where thepolyisobutenyl group has a number average weight of 1325) andethylenediamine, 140 g diluent lubricating oil and 850 ml xylenes. Thereaction mixture was then sparged with 13.3 liters of SO₂ over a60-minute period. During the addition of the SO₂, the reactiontemperature rose from 20° C. to 33° C. At the end of the SO₂ addition,the reaction mixture was brought to reflux (132° C.) and sparged withnitrogen for 60 minutes. Solvents were removed by stripping to 150° C.and 12 mm Hg. The product was diluted with 459 g of diluent lubricatingoil. The final product weighed 1200 g and contained 0.93L % N and 1.02%S.

EXAMPLE 4

A 5-liter reaction flask was charged with 993 g xylenes, 500 g of asuccinimide obtained by reacting two mols of a polyisobutenyl succinicanhydride of about 1100 MW with one mol of triethylenetetramine and 493g diluent lubricating oil. While stirring at 130° C., 12.4 liters of SO₂was bubbled through the reaction mixture over a 2-hour period. Thereaction was stirred for another hour at 130° C., then for 15 hours atambient temperatures. The reaction mixture was stripped to 160° C./2 mmHg for 0.5 hours to give 983 g of product (N=1.56%, S=0.50%).

EXAMPLE 5

A 2-liter reaction flask was charged with 483 g xylenes and 483 g of asuccinimide prepared by reacting 1.1 mol of a polyisobutylene succinicanhydride of about 400 MW with one mol of triethylenetetraamine. Whilestirring at 130° C., 9.0 liters of SO₂ was bubbled through the reactionmixture over a period of 90 minutes. The reaction was stirred at 130° C.for another 120 minutes, then stripped to 155° C./0.5 mm Hg for 0.5 hourto give 441 g of product (N=3.47%; S=1.97%).

EXAMPLE 6

A 2-liter reaction flask was charged with 487 g xylenes and 487 g ofAmoco 9250 (1.15% N; a borated Mannich dispersant prepared by reacting apolyisobutenyl-substituted phenol with formaldehyde and a polyamine andthen borating). While stirring at 130° C., 5.4 liters SO₂ wasintroducing over a 54-minute period. The reaction mixture was stirred at130° C. for 4 hours before introducing another 5.4 liters SO₂. Thecontents were stirred at 130° C. for another 16 hours and then strippedto give 482 g of product (N=1.06; S=11.1).

EXAMPLE 7

A 1-liter reaction flask was charged with 190 g xylenes and 190 g of apoly(oxyalkylene)aminocarbamate prepared by reacting ahydrocarbyl-capped poly(butylene oxide) chloroformate of approximately1400 MW with ethylenediamine. While stirring at 130° C., 1.7 liters SO₂was introduced over a period of 34 minutes. The reaction mixture wasstirred an additional 3 hours at 130° C., then stripped to 150° C./2.5mm Hg for 0.5 hour. Recovered was 193 g of product (N=1.28%, S=0.74%)

EXAMPLE 8

To a 10-gallon stainless-steel reactor was charged 7905 g of acommercial succinimide dispersant composition prepared frompolyisobutenyl succinic anhydride (where the polyisobutenyl group has anumber average molecular weight of 980) and triethylenetetraamine in7905 g of lubricating oil diluent. The mixture was heated to 130° C.under nitrogen and 633 g SO₂ was added over a period of 80 minutes. Thetemperature increased to 135° C. and the reactor pressure reached 1.36kg. At the end of the SO₂ addition, the product was sparged for 120minutes with nitrogen. The product was filtered to give 12,000 g ofmaterial containing 2.08% N and 1.50% S.

EXAMPLE 9

To a 500-ml reaction flask was added 88 g of a commercial succinimidedispersant composition prepared from polyisobutenyl succinic anhydride(where the polyisobutenyl group has a number average molecular weight ofabout 980) and tetraethylenepentamine and 112 g diluent lubricating oil.The mixture was heated to 150° C. with stir-ring. The mixture wassparged with SO₂ at the rate of 220 cc SO₂ /minute for 10 minutes,followed by sparging with nitrogen for 10 minutes. The product contained1.92% N and 1.12% S.

EXAMPLE 10

To a 1-liter stirred autoclave was charged 22 g of anamine-functionalized ethylene-propylene rubber of 30,000-200,000 MW in178 g of lubricating diluent oil. The mixture was warmed to 120° C. and2.44 g SO₂ was added. The reaction mass was stirred at 120° C. for 1hour, then sparged with nitrogen for 30 minutes at 120° C. The productcontained 0.06% N and 0.11 S.

EXAMPLE 11

To a 1-liter stirred autoclave was added 200 g of an amide detergentcomposition prepared from an aliphatic carboxylic acid of approximately280 molecular weight and tetraethylenepentamine (where the ratio ofcarboxylic acid to polyamine is approximately 3 to 1). The mixture washeated to 120° C. under nitrogen and 22.76 g of SO₂ was added. Thereaction mass was stirred at 120° C. for one hour, then sparged withnitrogen for 30 minutes at 120° C. The product contained 5.7% N and2.86% S.

EXAMPLE 12

The compositions of this invention were tested in a Caterpillar 1-G2test in which a single-cylinder diesel engine having a 51/8" bore by61/2" stroke is operated under the following conditions: timing, degreesBTDC, 8; brake mean effective pressure, psi 141; brake horsepower 42;Btu's per minute 5850; speed 1800 RPM; air boost, 53" Hg absolute, airtemperature in, 255° F.; water temperature out, 190° F.; and sulfur infuel, 0.4% w. At the end of each 12 hours of operation, sufficient oilis drained from the crankcase to allow addition of 1 quart of new oil.In the test on the lubricating oil compositions of this invention, the1-G2 test is run for 120 hours. At the end of the noted time period, theengine is dismantled and rated for cleanliness. The Institute ofPetroleum Test Number 247/69 merit rating system for engine wear andcleanliness, accepted by ASTM, API and and SAE, is the rating systemused to evaluate the engine. The over-all cleanliness is noted as WTD,which is the summation of the above numbers. Lower values representcleaner engines.

The base oil used in these tests is a mid-Continent base stock SAE 30oil containing 18 mmols/kg of a zinc dihydrocarbyl dithiophosphate, 37mmols/kg of a calcium phenate, and the amount noted in the table ofdetergent.

    ______________________________________                                        Test Results - 1-G2 Caterpillar Test (120 Hours)                                                                Un-                                                                           der-                                        Detergent   Grooves     Lands     head WTD                                    ______________________________________                                        1. 8% succinimide                                                                         55.6-7.1-1.8-0.9                                                                          485-170-55                                                                              5.2  424                                    derived from poly-                                                                        72.3-6.3-2.1-1.1                                                                          565-240-75                                                                              5.8  605                                    isobutenyl succinic                                                           anhydride & triethyl-                                                         enetetraamine in oil                                                          (50% actives)                                                                 (duplicate runs)                                                              2. 8% product of                                                                          73.3-3.8-1.8-0.7                                                                          290-80-25 4.0  355                                    Example 2* (50%                                                               actives)                                                                      3. 5% hydrocarbyl                                                                         65.7-5.1-1.6-1.0                                                                          440-210-110                                                                             7.9  515                                    polyamine prepared                                                            from polyisobutyl-                                                            ene chloride &                                                                ethylenediamine                                                               (80% actives).                                                                4. 8% Product of                                                                          70.0-4.5-1.3-0.9                                                                          330-65-60 6.7  399                                    Example 3 (50%                                                                actives)                                                                      ______________________________________                                         *The succinimide used as starting material in Example 2 is identical to       that tested in Test No. 1 above.                                         

These test results illustrate the superiority of the products of thisinvention in their ability to promote cleanliness of the engine and inparticular their ability to deter formation of deposits on the lands.

What is claimed is:
 1. A process for preparing a lubricating oiladditive which consists essentially of reacting at a temperature of from20° to 200° C. an oil-soluble amine-substituted hydrocarbon polymerviscosity index improver dispersant containing at least one primary orsecondary amino group, wherein said hydrocarbon polymer is selected froman ethylene-propylene copolymer or terpolymer, with from 0.2 to 2 molsof SO₂ for every 2 mols of basic nitrogen present in said dispersant. 2.A lubricating oil additive prepared according to the process of claim 1.3. A lubricating oil composition comprising an oil of lubricatingviscosity and from 0.1 to 10 percent by weight of the additive accordingto claim 2.